Suggestions followed by reasoning.
1. Implement an hourly reward system based on the hourly point tics.
One of the problems in cyrodiil is the lack of incentive to play the map. AP can be better achieved in other ways. The end of campaign rewards is too far and few and too small to truly motivate people to play the map. Everyone who plays the map does it for love of the game, probably knowing that they could earn greater rewards doing other things. Make it so that each score update two things are rewarded. First, reward having the most points of the three alliances. Second, reward an alliance who has improved their hourly tic score by a certain impressive amount of points. This will cause players to want to gain and hold territory rather than AP farming and flipping keeps back and forth.
2. Make the campaigns end with a bang, not a whimper. (MY BIGGEST SUGGESTION!!)
Do SOMETHING to make the end of a campaign exciting. Right now, end of campaigns are meaningless. At a certain point a comeback becomes impossible, so everybody is killing time waiting for the next campaign knowing that each keep capture or defense is meaningless beyond personal AP. Make something happen in the end that is crucial. It could be as simple has a small window of all score objectives are worth 10 times the amount for the last 5% of the campaign duration, or it could be something as spectacular as special map objectives with huge payoffs. Let the team going into the event with the lead have the advantage, but make a window at the end of the campaign to where the war climaxes with a bang and huge reversals are possible, rather than whimper out into boredom. Make me plan my schedule around the exciting campaign event because its that awesome!
3. Restrict people to one siege weapon.
Saved this controversial one for last. But part of the problem in Cyrodiil (depending on your view) is how fast a SMALL well organized team can take a keep. I could swear I've seen them take down a keep door in 2 minutes, but time perception might be skewed in battle. I am all for a good organized team winning. Organization and skill ought to carry the day. The problem is not that it can carry the day, but in how fast it can sweep a map. Right now, a team that really knows what it is doing, can have five people manning ballistas and simultaneously basically fully manning a battering ram. Throw in an outer ring of five people double or triple manning catapults/ballistaes, and you can have a ten man team possibly maxing a siege weapon cap on a door that is already too easily caved in. A perfectly organized team can do this so fast that you can turn away for mere moments and the castle is popped. You can go do a farm defense and find that two castles and an outpost behind you has flipped. Once again, problem is not that a good team can do it, but in how fast. The end result is that staying in a castle to defend it (assuming its not your last emperor keep) is strategically foolish. You can do too much running from keep to keep. We have guild log on, sweep the map in an hour, and log off, because its not worth it to hold ground when another group is not set up to do the sweeping. You could fix this by buffing keep health, but then you make it too tedious for unorganized groups to try and take a keep. Best solution, one siege weapon manning at a time. Simply make the siege weapons not reload on their own perhaps.
End result of these three things will be people actually playing to take and hold territory, not merely to capture and move on. Cheers.